Avian Migration: The Ultimate Red-Eye Flight

Many species of passerine bird migrate at night, which requires a complete turn-around in their circadian rhythm. In order to cover thousands of miles, their bodies shift into a metabolic state that would be considered obese and diabetic by human standards. Nocturnal migratory birds push the bounds of what we think is humanly possible: During migration, they stay awake night and day without cognitive loss. And they gorge themselves but perform like top atheletes. How and why do they do it?